User manual

Operation
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When the return air humidity reaches the end of the proportional band, either 100% or -100%, full
dehumidification or full humidification capacity is provided. No operation is performed when a 0%
call is calculated. The control varies the call for dehumidifying and humidifying in 1% increments as
the return air humidity moves through the proportional band halves.
The deadband range is used to widen the setpoint. When the return air humidity falls within the
deadband, the control operates the same as if the humidity equaled the setpoint exactly. This setting
helps maximize component life by preventing excessive component cycling. The Humidity
Proportional Band and Humidity Deadband parameters are in the Service menu under the Setpoints
submenu. The Humidity Setpoint parameter is in both the User menu and Service menu under
Setpoints.
3.5.1 Humidification
Infrared Humidifier
There are two types of infrared humidifiers: small pan (IFS) and large pan (IFL). The operating mode
of each is similar, however, some of the variables or timings differ. The Liebert Challenger has
different fill times because of the size of the pan.
Infrared humidifiers are started at 100% humidification request, and stopped at 0%. Infrared
humidifiers cannot be driven in proportional mode.
An autoflush system automatically controls a water makeup valve to maintain proper levels in the
infrared humidifier water pan during humidifier operation. If humidification is needed and 15 hours
have elapsed since the last time the humidifier was on, then the humidifier is not turned on until the
valve completes an initial fill of the humidifier pan. This pre-fill is about 30 seconds for a small pan
and 60 seconds for a large pan. The valve continues to fill and flush the pan for about 4-1/2 minutes
for a small pan or 7-1/2 minutes for a large pan. Pan size is selected based on unit specifications and
is preset at the factory.
During humidifier operation, with the flush rate set at the default of 150%, the valve is opened
periodically to add water to the pan (about 45 seconds every 7 minutes of humidifier operation for a
small pan, or 80 seconds every 10 minutes of operation for a large pan). This adds enough water to the
pan to cause about a third of the total water used to be flushed out of the overflow standpipe located
in the humidifier pan. This action helps to remove solids from the pan. The flush rate is adjustable
from 110% to 500% in 10% intervals. Default is 150%. If the water quality is poor, it may be desirable
to increase the water flushing action above the normal 150% rate. Also, if the supply water pressure
is low, the flush rate adjustment can be increased so that sufficient water level is maintained during
humidification. The flush rate parameter, Infrared Flush Rate (Service Menu, Options Setup), is
adjustable from 110%-500%.
External Humidifier Control—Optional
A factory-supplied option may be provided to allow a start-stop command to be sent to the control of a
remote-mounted humidifier.
Steam Generating Canister Humidifier
The Steam Generating Humidifier has its own separate control board that manages the canister and
steam rate. Liebert iCOM sends an On-Off command to relay a call for humidification.
Table 5 Parameters for infrared humidifier control
Parameter
IFS Default IFL Default
Liebert
Challenger
Humidity in Last xx Hours 15 hours 15 hours 15 hours
Fill Time 33 seconds 56 seconds 27 seconds
Humidifier On Time 440 seconds 576 seconds 568 seconds
Flush Rate 150% 150% 150%